As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIT - FLT 721 - CAPTAIN REPORTED AIRCRAFT WOULD NOT PRESSURIZE AFTER TAKEOFF. FLIGHT RETURNED TO FIELD AT PIT AND LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE CABIN PRESSURE CONTROLLER. PERFORMED PRESSURIZATION TEST AND CHECKED OPERATION OF OUTFLOW VALVE IN MANUAL PER MM 21-31-00. OPERATIONAL CHECK GOOD. (M)